1. Field of the Invention
The present invention relates to a method for manufacturing a mounting substrate and a method for manufacturing a circuit device, which include electroplating of a number of electrodes.
2. Description of the Related Art
Along with high integration of semiconductor elements, there has been a rapid increase in the number of pins of a circuit device including semiconductor elements mounted thereon. As countermeasures to realize an integrated circuit package with an increased number of pins, an external lead pitch has been reduced from 0.65 mm to about 0.5 mm in a conventional circuit device. Meanwhile, as the semiconductor elements have become highly integrated and multifunctional, a package of semiconductor elements of about 500 to 1000 pins has been desired.
Moreover, in order to protect a metal portion of a substrate for electronic components or to facilitate joining with other electronic components, partial plating has been conventionally performed for specific spots of the metal portion. There are various kinds of such plating. Here, as typical plating, wet electroplating and electroless plating can be enumerated. Generally, a stronger plated film can be formed by the electroplating than the electroless plating. In order to perform the electroplating, it is required to energize a member to be plated.
With reference to FIGS. 7A and 7B, description will be given of a conventional mounting substrate and a circuit device. FIG. 7A is a cross-sectional view of a circuit device 100, and FIG. 7B is a back view of FIG. 7A.
With reference to FIG. 7A, electrodes 104 made of copper foil or the like are formed on an upper surface of a mounting substrate 101 made of glass epoxy or the like. On a back of the mounting substrate 101, back face electrodes 105 are formed, which are connected to the electrodes 104 through via holes 106. Moreover, each of the electrodes 104 and the back face electrodes 105 is covered with a plated film 109. Here, in consideration of bonding properties of the electrodes 104 that are bonding pads, the plated film 109 is formed by electroplating.
A circuit element 102 that is a semiconductor element is fixed on the mounting substrate 101 and is connected to the electrodes 104 by use of metal thin wires 103. Moreover, a sealing resin 107 is formed so as to cover the circuit element 102.
With reference to FIG. 7B, on the back of the mounting substrate 101, the back face electrodes 105 are arranged in two rows parallel to a peripheral part of the mounting substrate 101. In order to perform the electroplating, the back face electrodes 105 are connected to the outside through plating wires 108. Moreover, the inner back face electrodes 105 are connected to the plating wires 108 which are drawn between the outer back face electrodes 105 to the outside. Accordingly, the back face electrodes 105 and the electrodes 104 are electroplated by energizing the back face electrodes 105 and the electrodes 104 via the plating wires 108.
However, in the foregoing circuit device 100, the plating wires 108 are drawn out between the outer back face electrodes 105. Therefore, when intervals between the back face electrodes 105 are, for example, about 0.5 mm, only one plating wire 108 can extend between the back face electrodes 105. Consequently, there was a problem that the back face electrodes 105 cannot be arranged in three rows or more.